Penetration of MeV electrons into the mesosphere accompanying pulsating aurorae

Abstract

Pulsating aurorae (PsA) are caused by the intermittent precipitations of magnetospheric electrons (energies of a few keV to a few tens of keV) through wave-particle interactions, thereby depositing most of their energy at altitudes ~ 100 km. However, the maximum energy of precipitated electrons and its impacts on the atmosphere are unknown. Herein, we report unique observations by the European Incoherent Scatter (EISCAT) radar showing electron precipitations ranging from a few hundred keV to a few MeV during a PsA associated with a weak geomagnetic storm. Simultaneously, the Arase spacecraft has observed intense whistler-mode chorus waves at the conjugate location along magnetic field lines. A computer simulation based on the EISCAT observations shows immediate catalytic ozone depletion at the mesospheric altitudes. Since PsA occurs frequently, often in daily basis, and extends its impact over large MLT areas, we anticipate that the PsA possesses a significant forcing to the mesospheric ozone chemistry in high latitudes through high energy electron precipitations. Therefore, the generation of PsA results in the depletion of mesospheric ozone through high-energy electron precipitations caused by whistler-mode chorus waves, which are similar to the well-known effect due to solar energetic protons triggered by solar flares.

Periodicities and Colors of Pulsating Auroras: DSLR Camera Observations From the International Space Station

“…By contrast, the B/G ratio distribution in Event 2 did not exhibit a similar characteristic. This tendency may be explained by the precipitation of high-energy electrons from the radiation belt, as reported by Miyoshi, Oyama, et al (2015) and Miyoshi et al (2020Miyoshi et al ( , 2021. As shown in the banana plots of Figures 3 and 4, the aurora oval was located   2 MLAT equatorward in Event 1 as compared with that in Event 2.…”

A Strong Correlation Between Relativistic Electron Microbursts and Patchy Aurora

“…However, no microburst precipitation was observed during their conjunction, notably when the SAMPEX footprint passed through pulsating aurora. A more recent study by Miyoshi et al (2021) reported an association between pulsating aurora and atmospheric ionization to altitudes as low as 65 km, likely caused by MeV electrons. The handful of studies showing correlation between the pulsating aurora and 1 MeV electrons suggest that the conditions to scatter MeV electrons are more stringent than the conditions to scatter keV electrons, and thus are harder to find (Lee et al, 2012;Summers, 2005).…”

Role of Ducting in Relativistic Electron Loss by Whistler‐Mode Wave Scattering

“…Chen, Gao, Lu, Tsurutani, & Wang, 2021) and within large-scale plasmasphere plumes (Woodroffe et al, 2017;Li et al, 2019;Demekhov et al, 2017Demekhov et al, , 2020, but also near smaller scale structures (Hanzelka & Santolík, 2019;Streltsov & Bengtson, 2020;Hosseini et al, 2021;Ke et al, 2021) which can be formed by compressional ultra-low-frequency waves or localized ionospheric outflows . Ducted chorus waves surviving with large amplitude and low obliquity at middle latitudes (off the equator), can potentially provide effective scattering of relativistic electrons as evidenced by modeling (L. Chen et al, 2020;Miyoshi et al, 2020Miyoshi et al, , 2021. To prove that this type of relativistic electron scattering and precipitation by whistlers actually occurs, it is not sufficient to observe the waves and relativistic electrons at the equator: it also requires confirmation that the waves are ducted, as evidenced by ground-based wave receivers (Manninen et al, 2013;Martinez-Calderon et al, 2015;Shiokawa et al, 2017), and that the relativistic electrons are precipitating, as measured at the ionosphere above the ground station.…”